Nissan Repair: 1993 Pathfinder SE 3.0 Knock sensor, fuel pressure regulator, nissan cars

Question
Suddenly my Pathfinder idles very rough as low as 300 rpm. Black acrid smoke is coming from the tail pipe. I took the truck in and they get a knock sensor problem. The truck seems to run fine at high rpm's on the hwy but as soon as it idles the truck almost dies. All plug wires and distributor have been replaced this year.
My first symptom of problems was that I was only getting 300 km per tank in the city.


Answer
Ron,

The knock sensor gives the computer information on timing and the engine advances or retards the engine accordingly.  Nissan cars do have problems with knock sensors after ten years or more.  I would replace the sensor.  Now, you will probably have another problem here with a plugged fuel filter or a stuck injector with regard to the black smoke.  This is commly called over-carburation.  Now, since you have fuel injection the problem is that you are getting too much gas and this can be caused by a faulty fuel pressure regulator, plugged fuel filter or a stuck open injector.  So, get the knock sensor replaced and the code cleared and then move on to what is giving the engine too much gas.